Exhaust pressure control valve

ABSTRACT

An exhaust pressure control valve to be placed in an exhaust gas passage of a diesel engine for controlling pressure of exhaust gas to be discharged from the engine comprise: a housing formed with a main passage and a bypass passage; a main valve arranged to open and close the main passage; a bypass valve arranged to open and close the bypass passage; and an opening/closing drive device for opening and closing the bypass valve. The opening/closing drive device includes: a positive pressure actuator for opening and closing the bypass valve by pressure upstream of the main passage; and a negative pressure actuator for changing valve opening pressure of the bypass valve.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2007-280329 filed on Oct. 29, 2007, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an exhaust pressure control valve provided in an exhaust passage of an engine to control pressure of exhaust gas to be discharged from the engine.

2. Description of Related Art

Heretofore, an exhaust pressure control valve for controlling pressure of exhaust gas has been proposed to enhance engine startability or purify exhaust gas to be discharged from an engine.

This type of exhaust pressure control valve has a housing provided with a main passage and a bypass passage. The main passage is formed with an inlet port and an outlet port opening in an inner wall. The inlet port communicates with an upstream end of the bypass passage and the outlet port communicates with a downstream end of the bypass passage. In the main passage, a throttle valve (a main valve) is placed to open and close the main passage. In the bypass passage, a bypass valve is placed to open and close the bypass passage. When this bypass valve is opened, exhaust gas is allowed to flow from an upstream side of the throttle valve to a downstream side of the throttle valve through the bypass passage.

This exhaust pressure control valve is arranged to open the bypass valve when an opening degree of the throttle valve is reduced and the pressure of exhaust gas increases and exceeds a predetermined value. When the bypass valve is opened, the exhaust gas will flow in the bypass passage. The pressure of exhaust gas is thus prevented from increasing and hence maintained at a predetermined value. When the opening degree of the throttle valve is increased, on the other hand, the pressure of exhaust gas decreases, closing the bypass valve and also the bypass passage (see WO 99/41495).

Recently, there has been studied application of such exhaust pressure control valve to a diesel particulate filter system (hereinafter, referred to as “DPF system”) for purifying exhaust gas to be discharged from a diesel engine. This DPF system is a device including a ceramic filter for trapping particulates matters (hereinafter, PM) contained in the exhaust gas in the diesel engine to purify the exhaust gas. In the DPF system, when an amount of PM trapped by the filter exceeds a fixed value, PM trapped by the filter is burnt to recover the filter. The exhaust pressure control valve is used for such filter recovery.

Specifically, when the filter is to be recovered, the opening degree of the throttle valve is reduced by the exhaust pressure control valve to increase the pressure of exhaust gas. When the pressure of exhaust gas exceeds a predetermined value (valve opening pressure of the bypass valve), the bypass valve is opened. Thus, the exhaust gas is allowed to flow in the bypass valve so that the pressure of exhaust gas is maintained at the predetermined value. An amount of fuel to be supplied to the engine is increased as the exhaust pressure increases. Accordingly, part of fuel unburnt in the engine will be supplied to an oxidation catalyst upstream of the filter. The fuel supplied to the oxidation catalyst will increase exhaust gas temperature in the catalyst by oxidation reaction and burn PM trapped in the filter, that is, recover the filter. After completion of recovering the filter, the throttle valve is opened and the exhaust pressure decreases to a normal level. The application of the exhaust pressure control valve to the DPF system therefore enables the filter recovery by use of the fuel to be supplied to the engine.

However, in the case of applying the aforementioned exhaust pressure control valve to the DPF system, a region would be narrow for the filter recovery. In other word, since the valve opening pressure of the bypass valve is constant (fixed), the exhaust pressure was kept at the predetermined value (the valve opening pressure of the bypass valve) during filter recovery.

Herein, if the exhaust gas temperature is high or the exhaust gas temperature has sufficiently increased during filter recovery, the filter can be recovered even if the exhaust pressure does not reach the predetermined value. Specifically, if only the exhaust gas temperature is high or the exhaust gas temperature has sufficiently risen during filter recovery, the filter can be recovered even if the exhaust pressure is lower than the predetermined value.

In the above exhaust pressure control valve, however, the valve opening pressure of the bypass valve is constant (fixed). Even when the exhaust gas temperature is so high as to enable filter recovery even though the exhaust pressure is lower then the predetermined value, the exhaust pressure is likely to be maintained at the pressure value (the valve opening pressure of the bypass valve) during filter recovery. This may increase the exhaust pressure more than necessary and consume an excessive amount of fuel to recover the filter, leading to low fuel economy. Furthermore, there is also a problem with deteriorated vehicle drivability.

BRIEF SUMMARY OF THE INVENTION

The present invention has an object to provide an exhaust pressure control valve capable of setting (or changing) more than one opening pressure of a bypass valve and capable of enhancing fuel economy and drivability.

Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

To achieve the purpose of the invention, there is provided an exhaust pressure control valve to be placed in an exhaust gas passage of an internal combustion engine for controlling pressure of exhaust gas to be discharged from the engine, the exhaust pressure control valve comprising: a housing formed with a main passage and a bypass passage; a main valve arranged to open and close the main passage; a bypass valve arranged to open and close the bypass passage; and an opening/closing drive device for opening and closing the bypass valve; wherein the opening/closing drive device includes: a bypass valve opening/closing device for opening and closing the bypass valve; and a valve opening pressure changing device for changing valve opening pressure of the bypass valve.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification illustrate an embodiment of the invention and, together with the description, serve to explain the objects, advantages and principles of the invention.

In the drawings,

FIG. 1 is a schematic diagram showing a configuration of an exhaust system of a diesel engine on which an exhaust pressure control valve of a first embodiment is mounted;

FIG. 2 is a sectional view of a schematic configuration of the exhaust pressure control valve;

FIG. 3 is a sectional view of the exhaust pressure control valve taken along a line III-III in FIG. 2;

FIG. 4 is a schematic diagram showing a positional relation between a bearing for a throttle shaft, an outlet port, and an inlet port in a circumferential direction;

FIG. 5 is a schematic configuration diagram of an opening/closing device for opening and closing a throttle valve;

FIG. 6 is a schematic configuration diagram of an opening/closing drive device for opening and closing a bypass valve;

FIG. 7 is a graph showing a pressure variation in a DPF device during filter recovery;

FIG. 8 is a graph showing a pressure variation in the DPF device during filter recovery;

FIG. 9 is a schematic configuration view of an opening/closing drive device of a second embodiment;

FIG. 10 is a schematic configuration view of an opening/closing drive device of a third embodiment;

FIG. 11 is a schematic configuration view of an opening/closing drive device of a fourth embodiment;

FIG. 12 is a schematic configuration view of an opening/closing drive device of a fifth embodiment; and

FIG. 13 is a schematic configuration view of an opening/closing drive device of a sixth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A detailed description of a preferred embodiment of an exhaust pressure control valve embodying the present invention will now be given referring to the accompanying drawings. This embodiment exemplifies the case where the exhaust pressure control valve of the invention is applied to a DPF system of a diesel engine.

First Embodiment

Firstly, a first embodiment will be described by explaining an exhaust system of a diesel engine on which the exhaust pressure control valve of this embodiment is mounted, referring to FIG. 1. FIG. 1 is a schematic configuration view of the exhaust system of the diesel engine on which the exhaust pressure control valve of the first embodiment is mounted.

As shown in FIG. 1, the exhaust system of the diesel engine includes a DPF device 3 and an exhaust pressure control valve 10. The DPF device 3 is placed upstream of the exhaust pressure control valve 10, that is, between the diesel engine 1 and the exhaust pressure control valve 10. A downstream end of the exhaust pressure control valve 10 is coupled to a muffler via an exhaust pipe 6.

This DPF device 3 includes a filter (made of ceramic) for trapping PM contained in exhaust gas. An upstream end of the DPF device 3 is coupled to the diesel engine 1 via an exhaust pipe 2. This exhaust pipe 2 is attached with a pressure sensor 2 a and an exhaust gas temperature sensor 2 b. This pressure sensor 2 a is to detect the pressure Pu of the exhaust gas flowing in the exhaust pipe 2. The exhaust gas temperature sensor 2 b is to detect the temperature T of exhaust gas flowing in the exhaust pipe 2, that is, temperature of exhaust gas (incoming gas) to be delivered to the DPF device 3. On the other hand, a downstream end of the DPF device 3 is coupled to the exhaust pressure control valve 10 via an exhaust pipe 5 which is attached with a pressure sensor 5 a. This pressure sensor 5 a is to detect the pressure Pd of exhaust gas flowing in the exhaust pipe 5. Exhaust gas pressure signals detected by the pressure sensors 2 a and 5 a and an exhaust gas temperature signal detected by the exhaust gas temperature sensor 2 b are inputted to an ECU (electronic control unit) 4 mentioned later.

The diesel engine 1 and the exhaust pressure control valve 10 are controlled by the ECU 4. This ECU 4 includes, as well known, a central processing unit (CPU), a random access memory (RAM), a read-only memory (ROM), etc. The ROM stores a program for controlling the diesel engine 1, a program for controlling the exhaust pressure control valve 10 during filter recovery in the DPF device 3, and other programs.

This ECU 4 is configured to control an amount of intake air and an amount of fuel to be supplied to the diesel engine 1 according to an operating condition of the engine 1. Furthermore, the ECU 4 is arranged to recover the filter of the DPF device 3 by closing the throttle valve 30 of the exhaust pressure control valve 10 mentioned later when a pressure difference between the pressures detected by the pressure sensors 2 a and 5 a (namely, a pressure loss of the DPF device 3) exceeds a predetermined value. Furthermore, when the exhaust gas temperature detected by the exhaust gas temperature sensor 2 b exceeds a predetermined value prior to or during recovery of the filter of the DPF device 3, the ECU 4 changes (lowers) a valve opening pressure of the bypass valve 26 of the exhaust pressure control valve 10 mentioned later. In this specification, the “valve opening pressure” represents the pressure required to open a valve. Thus, the higher the valve opening pressure, the larger the valve closing force is.

Herein, the exhaust pressure control valve 10 will be described with reference to FIGS. 2 to 4. FIG. 2 is a sectional view of a schematic configuration of the exhaust pressure control valve. FIG. 3 is a sectional view of the same taken along a line III-III in FIG. 2. FIG. 4 is a schematic view showing a positional relation between a bearing for a throttle shaft, an outlet port, and an inlet port in a circumferential direction.

The exhaust pressure control valve 10 is a device for controlling the pressure of exhaust gas to be discharged from the diesel engine 1. As shown in FIG. 2, the exhaust pressure control valve 10 includes a housing 11, the throttle valve (a main valve) 30 for opening/closing a main passage 12, and a bypass valve 26 for opening/closing a bypass passage 28.

The housing 11 is formed with the main passage 12 and the bypass passage 28 arranged adjacent to the main passage 12. An upstream end 14 of the main passage 12 is connected to the exhaust pipe 5. An inlet port 16 and an outlet port 46 are formed to open in an inner wall of main passage 12. The inlet port 16 is located closer to the upstream end 14 and the outlet port 46 is located closer to a downstream end 66. The throttle valve 30 is placed between those inlet port 16 and outlet port 46. This throttle valve 30 is configured to open and close the main passage 12 between the inlet port 16 and the outlet port 46.

A throttle shaft 32 of the throttle valve 30 is placed passing the center (a point O) of the main passage 12 as shown in FIG. 4 and both ends thereof are supported by the wall (points A and B of the housing 11) of the main passage 12 respectively. The throttle valve 30 is a butterfly valve as shown in FIG. 2 and includes the throttle shaft 32 and a valve element 34 attached to the throttle shaft 32. This throttle valve 30 is configured to change by rotation of the throttle shaft 32 between a state where the valve element 34 closes the main passage 12 and a state where the valve element 34 opens the main passage 12. In the state for closing the main passage 12, the valve element 34 is held to be tilt with respect to an axial line (a central axis) of the main passage 12 (see FIG. 3). Furthermore, a clearance is produced between the periphery edge of the valve element 34 and the inner wall surface of the main passage 12. This clearance is provided enough to enable operation of the diesel engine 1 even when the throttle valve 30 is closed. The clearance is formed along the entire periphery of the valve element 34.

A support end 32 a which is one end of the throttle shaft 32 is rotatably supported by a bearing 40 which is mounted in a hole 42 formed in the housing 11. This hole 42 is located between the inlet port 16 and the outlet port 46. The hole 42 has an end (closer to the main passage 12) in which the throttle shaft 32 is inserted and the other end formed to open in the bypass passage 28 but closed by a cap 36. The cap 36 closing the opening of the hole 42 serves to prevent PM in exhaust gas from entering the hole 42.

The other end of the throttle shaft 32 is rotatably supported by a bearing 54 which is mounted in a hole 52 formed in the housing 11. The hole 52 has one end (closer to the main passage 12) through which the throttle shaft 32 is inserted. Seal rings 50 are fitted on the throttle shaft 32 in the hole 52 to prevent exhaust gas from leaking out of the main passage 12. The hole 52 also has the other end formed to open outside, through which a drive end 32 b of the throttle shaft 32 protrudes out. The drive end 32 b of the throttle shaft 32 is coupled to a rod 60 of an actuator 64 via a connecting member 62. When the rod 60 is moved, the throttle shaft 32 is rotated.

The position of the inlet port 16 in the circumferential direction is aligned with the position of the bearing that supports the end (32 a) of the throttle shaft 32 in the circumferential direction (the point A or B in FIG. 4). As with the inlet port 16, the position of the outlet port 46 in the circumferential direction is also aligned with the position of the bearing that supports the end (32 a) of the throttle shaft 32 in the circumferential direction. Thus, the main passage 12 and the bypass passage 28 extend in nearly parallel with each other.

The inlet port 16 is formed in circular section so as to be easily closed hermetically by the bypass valve 26 (see FIG. 2). On other hand, the outlet port 46 is formed in rectangular section so as to ensure a large passage sectional area, thereby allowing exhaust gas to easily flow in the main passage 12 through the outlet port 46. As shown in FIG. 2, a wall surface 48 downstream of the outlet port 46 has a curved (rounded) surface continuous to the main passage 12. This makes it easy for the exhaust gas flowing from the bypass passage 28 into the main passage 12 to flow toward the downstream end 66.

The bypass passage 28 has an upstream end communicating with the main passage 12 through the inlet port 16 and a downstream end communicating with the main passage 12 through the outlet port 46. In this bypass passage 28, the bypass valve 26 is placed to open and close an opening of the inlet port 16 communicating with the bypass passage 28. This bypass valve 26 is placed in a position back from the inner wall surface of the main passage 12. The bypass valve 26 is a flapper valve including a valve element 24 and a bolt 22 with which the valve element 24 is attached to an arm 20.

Next, the opening/closing device for opening and closing the throttle valve 30 will be explained referring to FIG. 5. FIG. 5 is a schematic configuration diagram of the opening/closing device for opening and closing the throttle valve 30. As shown in FIG. 5, the opening/closing device 41 for opening and closing the throttle valve 30 includes an actuator 64, a three-way electromagnetic valve 47, and a vacuum pump 43.

The actuator 64 is a diaphragm actuator including a cylinder 67 and a rod 60. The rod 60 includes a partition wall 60 a provided at its proximal end and a rod portion 60 b vertically provided on the partition wall 60 a.

The partition wall 60 a is movably housed in the cylinder 67 and thereby a pressure chamber 68 is defined in the cylinder 67. The pressure chamber 68 communicates with a neutral port 47 c of the three-way electromagnetic valve 47 through a pipe 55. Of two remaining ports of the three-way electromagnetic valve 47, a port 47 a is connected to the vacuum pump 43 and a port 47 b is connected to atmosphere. In the pressure chamber 68, a spring 69 is set in a compressed state. This spring 69 urges the partition wall 60 a in an opposite direction to the pressure chamber 68.

A distal end of the rod 60 is attached with the rotatable connecting member 62. When the rod 60 is moved forward or backward (laterally in FIG. 5), the throttle shaft 32 is rotated accordingly, thereby changing the throttle valve 30 between a state for opening the main passage 12 and a state for closing the main passage 12. In other words, when the pressure in the pressure chamber 68 of the actuator 64 exceeds a predetermined pressure, the throttle valve 30 is made to open the main passage 12. When the pressure in the pressure chamber 68 of the actuator 64 decreases the predetermined pressure or less, the throttle valve 30 is made to close the main passage 12.

The three-way electromagnetic valve 47 is connected to the ECU 4 and controlled based on a command from the ECU 4. When the port 47 b is closed and the neutral port 47 c and the port 47 a are allowed to communicate with each other and then the vacuum pump 43 is activated, the air in the pressure chamber 68 of the actuator 64 is discharged. Thus, the throttle valve 30 is brought in the closing state. On the other hand, when the port 47 a is closed and the neutral port 47 c and the port 47 b are allowed to communicate with each other, atmospheric air is introduced in the pressure chamber 68 of the actuator 64. The throttle valve 30 is brought in the opening state.

An opening/closing drive device for opening and closing the bypass valve 26 will be explained below referring to FIG. 6. FIG. 6 is a schematic configuration diagram of the opening/closing drive device for opening and closing the bypass valve 26. As shown in FIG. 6, the opening/closing drive device 70 includes a positive pressure actuator 71, a negative pressure actuator 72, and a link mechanism (73, 20) for transmitting motions of the actuators 71 and 72 to the bypass valve 26.

The positive pressure actuator 71 is a diaphragm actuator, which is one example of a “bypass valve opening/closing device” of the invention. This positive pressure actuator 71 includes a cylinder 80 and a rod 81. The rod 81 includes a partition wall 81 a at its proximal end and a rod portion 81 b vertically provided on the partition wall 81 a.

The partition wall 81 a is movably housed in the cylinder 80 and thereby the cylinder 80 is divided into a pressure chamber 82 and a spring chamber 83. The pressure chamber 82 communicates with the exhaust pipe 5 through an exhaust pressure introduction pipe 23 so that exhaust gas flowing in the pipe 5 is introduced into the pressure chamber 82. In the spring chamber 83, a spring 84 is set in a compressed state. This spring 84 urges the partition wall 81 a toward the pressure chamber 82.

A distal end of the rod portion 81 b is connected with a rotatable proximal end of the link 73. A distal end of the link 73 is fixed to one end of the arm 20. The other end of the arm 20 is attached with the bypass valve 26. While the pressure of exhaust gas introduced in the pressure chamber 82 is equal to or less than a predetermined valve opening pressure (two values are set in this embodiment), the resultant urging force of the spring 84 and a spring 94 mentioned later acting on the partition wall 81 a or the urging force of only the spring 84 acting on the partition wall 81 a is larger than the pressure of the exhaust gas in the pressure chamber 82 acting on the partition wall 81 a. At that time, the rod 81 is in an initial position where the bypass valve 26 closes the bypass passage 28. When the pressure of exhaust gas introduced in the pressure chamber 82 exceeds the predetermined valve opening pressure, on the other hand, the rod 81 is moved forward (downward in FIG. 6) against the urging force of the spring 84 and the spring 94 or the urging force of only the spring 84. Accordingly, the arm 20 is rotated about the shaft 18 and the bypass valve 26 attached to the distal end of the arm 20 is moved to open the bypass passage 28.

The negative pressure actuator 72 is a diaphragm actuator, which is one example of a “valve opening pressure changing device” of the invention. This negative pressure actuator 72 includes a cylinder 90 and a rod 91. The rod 91 includes a partition wall (a movable member) 91 a provided at a proximal end and a rod portion 91 b vertically provided on the partition wall 91 a. The partition wall 91 a is movably housed in the cylinder 90 and thereby the cylinder 90 is divided into two compartments. One of the compartments divided by the partition wall 91 a is a pressure chamber 92 located opposite the rod portion 91 b. The pressure chamber 92 communicates with a neutral port 96 c of a three-way electromagnetic valve 96 through a pipe 95. Of two remaining ports of the three-way electromagnetic valve 96, a port 96 a is connected to a vacuum pump 97 and a port 96 b is connected to atmosphere. In the pressure chamber 92, a spring 94 is set in a compressed state. This spring 94 urges the partition wall 91 a in a direction (upward in FIG. 6) opposite to the pressure chamber 92.

This negative pressure actuator 72 is placed opposite the positive pressure actuator 71, that is, placed to face the positive pressure actuator 71. More concretely, the rod portion 91 b is placed coaxial with the rod portion 81 b so that a distal end of the rod portion 91 b is in contact with a distal end (the end of the link 73) of the rod portion 81 b.

The three-way electromagnetic valve 96 is connected to the ECU 4 and controlled based on a command from the ECU 4. When the port 96 b is closed and the neutral port 96 c and the port 96 a are allowed to communicate with each other and then the vacuum pump 97 is activated, the air in the pressure chamber 92 of the negative pressure actuator 72 is discharged. This causes the rod 91 to move backward (downward in FIG. 6) into the cylinder 90, separating the distal end of the rod portion 91 b from the distal end (the end of the link 73) of the rod portion 81 b. When the port 96 a is closed and the neutral port 96 c and the port 96 b are allowed to communicate with each other, on the other hand, atmospheric air is introduced in the pressure chamber 92 of the negative pressure actuator 72. This causes the rod 91 to move forward (upward in FIG. 6) to thereby bring the distal end of the rod portion 91 b into contact with the distal end (the end of the link 73) of the rod portion 81 b.

While the distal end of the rod portion 91 b is in contact with the distal end (the end of the link 73) of the rod portion 81 b, the urging force of the spring 94 acts on the partition wall 81 a through the rod portions 91 b and 81 b. Accordingly, the urging forces (the resultant urging force) of the springs 84 and 94 act on the partition wall 81 a of the positive pressure actuator 71. In other words, the urging force of the spring 94 serves to reinforce or increase the urging force of the spring 84 against the partition wall 81 a, thereby increasing the valve opening pressure of the bypass valve 26. While the distal end of the rod portion 91 b is out of contact with the distal end of the rod portion 81 b, on the other hand, the urging force of the spring 94 does not act on the partition wall 81 a. Thus, the urging force of only the spring 84 acts on the partition wall 81 a of the positive pressure actuator 71.

The opening/closing drive device 70 is arranged as above to switch the negative pressure actuator 72 between an inactive state and an active state in order to change the urging force that acts on the partition wall 81 a of the positive pressure actuator 71, namely, the valve opening pressure of the bypass valve 26 (two stages (75 kPa and 150 kPa) in this embodiment). Accordingly, the valve opening pressure of the bypass valve 26 is set at a high valve opening pressure (hereinafter, “high pressure”) P1 (150 kPa in this embodiment) during the inactive state (the initial state) of the actuator 72 and at a low valve opening pressure (hereinafter, “low pressure”) P2 (75 kPa in this embodiment) during the active state of the actuator 72.

The opening/closing drive device 70 can change the valve opening pressure of the bypass valve 26 in multiple stages (two stages in this embodiment) by the negative pressure actuator 72 simply and inexpensively configured as above. The positive pressure actuator 71 and the negative pressure actuator 72 constituting the opening/closing drive device 70 are simple in structure and hence superior in reliability. The opening/closing drive device 70 can also provide high reliability.

Operations of the DPF system of the diesel engine having the above configurations are explained below.

The exhaust gas discharged from the diesel engine 1 is allowed to flow in the DPF device 3 through the exhaust pipe 2. The DPF device 3 traps PM contained in the exhaust gas to purify the exhaust gas. The exhaust gas purified by the DPF device 3 is allowed to pass through the exhaust pipe 5, the exhaust pressure control valve 10, and the exhaust pipe 6, and the exhaust gas is then discharged to atmosphere through the muffler.

As PM are trapped and accumulated in the DPF device 3, the pressure loss of the DPF device 3 will increase. When the pressure loss exceeds a predetermined value, the throttle valve 30 of the exhaust pressure control valve 10 is closed by the ECU 4. To be more concrete, the ECU 4 outputs a drive signal to the three-way electromagnetic valve 47 to close the port 47 b and allow communication between the neutral port 47 c and the port 47 a. Then, the vacuum pump 43 is activated. The air in the pressure chamber 68 of the actuator 64 is discharged, causing the throttle valve 30 to close the main passage 12.

When the throttle valve 30 closes the main passage 12 as above, the exhaust pressure in the diesel engine 1 increases. Accordingly, the pressure of exhaust gas introduced in the pressure chamber 82 of the positive pressure actuator 71 which drives the bypass valve 26 also increases. When the pressure of exhaust gas in the pressure chamber 82 exceeds the predetermined value (the valve opening pressure), the rod 81 is moved forward (downward in FIG. 6) against the urging force of the spring 84. Thus, the bypass valve 26 opens the bypass passage 28. The valve opening degree of the bypass valve 26 depends on the pressure of exhaust gas in the exhaust pipe 5. The higher the pressure of exhaust gas in the exhaust pipe 5, the larger the valve opening degree will be. To the contrary, the lower the pressure of exhaust gas in the exhaust pipe 5, the smaller the valve opening degree will be. When the pressure of exhaust gas in the pressure chamber 82 decreases to the predetermined value (the valve opening pressure) or less, the rod 81 is moved backward (upward in FIG. 6) into the cylinder 80 by the urging force of the spring 84, causing the bypass valve 26 to close the bypass passage 28. Then, the pressure of exhaust gas in the exhaust pipe 5 will increase accordingly. By such operation of the bypass valve 26, the pressure of exhaust gas in the exhaust pipe 5 is maintained almost constant while the throttle valve 30 is closing the main passage 12.

The bypass valve 26 is located in a position back from the inner wall surface of the main passage 12. Accordingly, the exhaust pressure of the main passage 12 will not directly act on the bypass valve 26. The bypass valve 26 are opened and closed when linear motion of the actuator 71 is transmitted to the arm 20 via the link mechanism. Consequently, the bypass valve 26 can behave stably even when the exhaust gas flowing in the exhaust pipe 5 causes pulsations, and thereby chattering of the bypass valve 26 can be prevented. This enables enhanced controllability of exhaust pressure.

While the throttle valve 30 closes the main passage 12, when the exhaust pressure in the diesel engine 1 rises and the pressure of exhaust gas in the exhaust pipe 5 is maintained almost constant, the engine power will decrease. To prevent such engine power decrease, an amount of fuel to be supplied to the engine 1 is increased. In short, when the throttle valve 30 is closed to increase the exhaust pressure in the engine 1, the amount of fuel to be supplied to the engine 1 is increased. As a result, the gas containing unburnt components is supplied to the DPF device 3 and hence to the oxidation catalyst upstream of the filter. The unburnt components supplied to the oxidation catalyst increase gas temperature in the catalyst by oxidation reaction. Thereby PM trapped by the filter is burnt. The filter of the DPF device 3 is thus recovered.

After completion of recovery of the filter of the DPF device 3, the ECU 4 opens the throttle valve 30 of the exhaust pressure control valve 10 and returns to a normal operating condition. Specifically, the ECU 4 outputs a drive signal to the three-way electromagnetic valve 47 to close the port 47 a and allow communication between the neutral port 47 c and the port 47 b. Consequently, atmospheric air is introduced in the pressure chamber 68 of the actuator 64 through the three-way electromagnetic valve 47, thereby moving the throttle valve 30 to open the main passage 12. The recovery of the filter of the DPF device 3 is performed every time when the pressure loss of the DPF device 3 exceeds the predetermined value.

Herein, in the conventional exhaust pressure control valve, the valve opening pressure of the bypass valve is fixed (constant). Even when the temperature of exhaust gas is so sufficiently high as that the filter recovery is enabled even though the pressure of exhaust gas is lower than the predetermined value, the pressure of exhaust gas would be kept at the predetermined value (the valve opening pressure of the bypass valve) during the recovery of the filter of the DPF device. This results in a state where the pressure of exhaust gas is increased more than necessary, deteriorating drivability and consuming an excessive amount of fuel for filter recovery, leading to a poor fuel economy.

On the other hand, the exhaust pressure control valve 10 of the present embodiment is provided with the positive pressure actuator 71 and the negative pressure actuator 72 in the opening/closing drive device 70 and arranged to switch the negative pressure actuator 72 between the active state and the inactive state to thereby change the urging force acting on the partition wall 81 a of the positive pressure actuator 71, that is, the valve opening pressure (in two stages (75 kPa and 150 kPa) in this embodiment) of the bypass valve 26. This valve opening pressure of the bypass valve 26 is changed from the high pressure P1 to the low pressure P2 when the exhaust gas temperature sensor 2 b detects a predetermined temperature or higher. The predetermined temperature at which the valve opening pressure of the bypass valve 26 is changed may be set at a temperature (e.g. about 225° C. to about 325° C.) enabling filter recovery if the valve opening pressure of the bypass valve 26 reaches the low valve opening pressure even, even if it does not reaches the high valve opening pressure (equal to the valve opening pressure of the conventional bypass valve).

In other words, in the opening/closing drive device 70, the negative pressure actuator 72 is initially in an inactive state where the urging forces of the springs 84 and 94 act on the partition wall 81 a of the positive pressure actuator 71. Accordingly, the valve opening pressure of the bypass valve 26 is set at the high pressure P1. When the exhaust gas temperature detected by the exhaust gas temperature sensor 2 exceeds the predetermined temperature, the ECU 4 activates the negative pressure actuator 72. Concretely, the ECU 4 outputs a drive signal to the three-way electromagnetic valve 96 to close the port 96 b and allow communication between the neutral port 96 c and the port 96 a. Successively, the vacuum pump 97 is activated. The air in the pressure chamber 92 of the actuator 72 is thus discharged, retracting the rod 91 into the cylinder 90 to separate the distal end from the rod 81 (the link 73). The urging force of only the spring 84 therefore acts on the partition wall 81 a of the positive pressure actuator 71. The valve opening pressure of the bypass valve 26 is changed to the low pressure P2 accordingly.

In the case where the exhaust gas temperature detected by the exhaust gas temperature sensor 2 b exceeds the predetermined temperature during filter recovery of the DPF device 3, as above, the valve opening pressure of the bypass valve 26 is set at the low pressure P2. The pressure in the DPF device 3 is consequently changed (decreased) from P1 to P2 during the filter recovery as shown in FIG. 7. Specifically, the pressure in the DPF device 3 is not maintained at P1, unlike the conventional one indicated by a chain line in FIG. 7. The exhaust pressure control valve 10 of this embodiment therefore will not cause a state where the pressure of exhaust gas is increased more than necessary. This makes it possible to enhance drivability and fuel economy. FIG. 7 is a graph showing a state where pressure in the DPF device varies during filter recovery.

When the exhaust gas temperature detected by the exhaust gas temperature sensor 2 b exceeds the predetermined temperature prior to or just after filter recovery of the DPF device 3, the filter recovery is conducted under the pressure of the DPF device 3 being “P2” from the beginning of the filter recovery, not from halfway. That is, the pressure in the DPF device 3 will not rise unlike the conventional one shown by a chain line in FIG. 8. It is therefore possible to further enhance the drivability and fuel economy during filter recovery of the DPF device 3. FIG. 8 is a graph showing a state where pressure in the DPF device varies during filter recovery.

The exhaust pressure control valve 10 of the present embodiment includes the negative pressure actuator 72 in the opening/closing drive device 70 for opening and closing the bypass valve 26 as mentioned above in detail. During the inactive state of the negative pressure actuator 72, the rod portion 91 b is held in contact with the distal end (the end of the link 73) of the rod portion 81 b of the positive pressure actuator 71, so that the spring 94 exerts a valve closing force on the bypass valve 26 to enhance the valve opening pressure. The valve opening pressure of the bypass valve 26 can therefore be set at the high pressure P1 (equal to the conventional valve opening pressure). During the active state of the negative pressure actuator 72, on the other hand, the rod portion 91 b is separated from the distal end (the end of the link 73) of the rod portion 81 b of the positive pressure actuator 71, thereby releasing the valve closing force from the bypass valve 26. The valve opening pressure of the bypass valve 26 can therefore be set at the low pressure P2 (lower than the conventional valve opening pressure). In the above way, the exhaust pressure control valve 10 can change the valve opening pressure of the bypass valve 26.

According to the exhaust pressure control valve 10, consequently, the valve opening pressure of the bypass valve can be reduced in the case where filter recovery is enabled because the temperature of exhaust gas is high or the temperature of exhaust gas has risen so sufficiently high during filter recovery. The pressure of exhaust gas therefore does not have to be increased more than necessary, unlike conventional configuration, the filter recovery does not need consumption of an excessive amount of fuel. This can improve fuel economy and prevent an increase in pressure of exhaust gas more than necessary. Thus, exhaust gas resistance lowers and hence vehicle drivability can be enhanced.

Second Embodiment

A second embodiment will be described below. This embodiment is substantially identical in configuration to the first embodiment excepting a configuration of an opening/closing drive device for opening and closing a bypass valve. The following explanation will be made on an exhaust pressure control valve of the second embodiment referring to FIG. 9 with a focus on differences from the first embodiment by using the same reference signs to similar or identical parts or components to those of the first embodiment. FIG. 9 is a schematic configuration view of an opening/closing drive device of the second embodiment.

As shown in FIG. 9, an opening/closing drive device 70 a includes the positive pressure actuator 71, the negative pressure actuator 72, and a link mechanism (73 a and 20) for transmitting motions of the actuators 71 and 72 to the bypass valve 26.

In this opening/closing drive device 70 a, a distal end of a link 73 a is fixed to one end of the arm 20. The other end of the arm 20 is attached with the bypass valve 26. The negative pressure actuator 72 is placed on the same side as and in parallel with the positive pressure actuator 71 so that the distal end of the rod portion 91 b can contact with the other end of the link 73 a opposite the distal end fixed to the arm 20. The positive pressure actuator 71 is rotatably attached, at a distal end of the rod 81, to the link 73 a between a portion fixed to the arm 20 and a portion contacting with the rod portion 91 b. The link 73 a is therefore longer the link 73 of the first embodiment. Thus, the negative pressure actuator 72 can be made compact as compared with that of the first embodiment.

In this opening/closing drive device 70 a, when the port 96 b of the three-way electromagnetic valve 96 is closed and the neutral port 96 c and the port 96 a are allowed to communicate with each other and then the vacuum pump 97 is activated, the air in the pressure chamber 92 of the negative pressure actuator 72 is discharged. This causes the rod 91 to move backward (upward in FIG. 9) into the cylinder 90, separating the distal end of the rod portion 91 b from the end of the link 73 a. On the other hand, when the port 96 a is closed and the neutral port 96 c and the port 96 b are allowed to communicate with each other, atmospheric air is introduced in the pressure chamber 92 of the negative pressure actuator 72. This causes the rod 91 to move forward (downward in FIG. 9) to thereby bring the distal end of the rod portion 91 b into contact with the end of the link 73 a.

While the distal end of the rod portion 91 b is in contact with the end of the link 73 a, the urging force of the spring 94 acts on the partition wall 81 a through the rod portion 91 b, link 73 a, and rod portion 81 b. At that time, the urging force of the spring 94 serves to weaken or reduce the urging force of the spring 84. On the other hand, when the distal end of the rod portion 91 b is separated from the end of the link 73 a, the urging force of the spring 94 does not act on the partition wall 81 a. Accordingly, the partition wall 81 a of the positive pressure actuator 71 receives the urging force of only the spring 84. The urging force of the spring 84 is designed to be higher than that in the first embodiment.

The opening/closing drive device 70 a is configured as above to switch the negative pressure actuator 72 between an active state and an inactive state to change the urging force acting on the partition wall 81 a of the positive pressure actuator 71, that is, to change the valve opening pressure of the bypass valve 26 (in two stages (150 kPa and 75 kPa) in this embodiment). Thus, the valve opening pressure of the bypass valve 26 is set at the high pressure P1 (150 kPa in this embodiment) when the negative pressure actuator 72 is in the active state (an initial state) and set at the low pressure P2 (75 kPa in this embodiment) when the negative pressure actuator 72 is in the inactive state.

In the exhaust pressure control valve of the second embodiment including the aforementioned opening/closing drive device 70 a, the negative pressure actuator 72 is initially in the active state when the filter of the DPF device 3 is to be recovered. The rod 91 is therefore in a retracted position in the cylinder 90 with its distal end being apart from the link 73 a. Accordingly, the urging force of only the spring 84 acts on the partition wall 81 a of the positive pressure actuator 71 and hence the valve opening pressure of the bypass valve 26 is set at the high pressure P1.

When the exhaust gas temperature detected by the exhaust gas temperature sensor 2 b exceeds the predetermined temperature, the ECU 4 stops activation of the negative pressure actuator 72. To be concrete, the ECU 4 stops outputting the drive signal to the three-way electromagnetic valve 96, allowing the port 96 b to open and the neutral port 96 c and the port 96 b to communicate with each other. Simultaneously, the vacuum pump 97 is also stopped. Then, the rod 91 is moved forward (downward in FIG. 9) by the urging force of the spring 94 to come into contact with the link 73 a. The urging force of the spring 94 acts on the partition wall 81 a of the positive pressure actuator 71 to weaken the urging force of the spring 84. Thus, the valve opening pressure of the bypass valve 26 is set at the low pressure P2.

In the exhaust pressure control valve of the second embodiment, as mentioned above, the rod portion 91 b is held in contact with the end of the link 73 a during the inactive state of the negative pressure actuator 72 of the opening/closing drive device 70 a for opening and closing the bypass valve 26, so that the spring 94 exerts a valve opening force on the bypass valve 26 to reduce the valve opening pressure thereof. Accordingly, the valve opening pressure of the bypass valve 26 can be set at the low pressure P2 (lower than the conventional valve opening pressure). During the active state of the negative pressure actuator 72, on the other hand, the rod portion 91 b is separated from the end of the link 73 a to release the valve opening force from the bypass valve 26. Accordingly, the valve opening pressure of the bypass valve 26 can be set at the high pressure P1 (equal to the conventional valve opening pressure). The exhaust pressure control valve of the second embodiment can therefore change the valve opening pressure of the bypass valve 26.

According to the exhaust pressure control valve of the second embodiment, consequently, the valve opening pressure of the bypass valve can be reduced in the case where filter recovery is enabled because the temperature of exhaust gas is high or the temperature of exhaust gas has risen so sufficiently high during filter recovery. The pressure of exhaust gas therefore will not increase more than necessary, unlike conventional configuration, the filter recovery does not need consumption of an excessive amount of fuel. This can improve fuel economy and prevent an increase in pressure of exhaust gas more than necessary. Thus, exhaust gas resistance lowers and hence vehicle drivability can be enhanced.

Third Embodiment

A third embodiment will be described below. This embodiment is substantially identical in configuration to the first embodiment excepting a configuration of an opening/closing drive device for opening and closing a bypass valve. The following explanation will be made on an exhaust pressure control valve of the third embodiment referring to FIG. 10 with a focus on differences from the first embodiment by using the same reference signs to similar or identical parts or components to those of the first embodiment. FIG. 10 is a schematic configuration view of an opening/closing drive device of the third embodiment.

As shown in FIG. 10, an opening/closing drive device 70 b includes the positive pressure actuator 71, the negative pressure actuator 72, and a link mechanism (73 b and 20) for transmitting motions of the actuators 71 and 72 to the bypass valve 26.

In this opening/closing drive device 70 b, the distal end of the rod portion 81 b of the positive pressure actuator 71 is rotatably attached to a proximal end of a link 73 b. The negative pressure actuator 72 is placed on the same side as and in parallel with the positive pressure actuator 71 so that the distal end of the rod portion 91 b can contact with a distal end of the link 73 b (opposite to the proximal end attached to the rod 81). One end of the arm 20 is fixed to the link 73 b between the positive pressure actuator 71 and the negative pressure actuator 72. The other end of the arm 20 is attached with the bypass valve 26. Accordingly, the link 73 b is longer than the link 73 of the first embodiment. Thus, the negative pressure actuator 72 can be made compact as compared with that of the first embodiment.

In this opening/closing drive device 70 b, when the port 96 b of the three-way electromagnetic valve 96 is closed and the neutral port 96 c and the port 96 a are allowed to communicate with each other and then the vacuum pump 97 is activated, the air in the pressure chamber 92 of the negative pressure actuator 72 is discharged. This causes the rod 91 to move backward (upward in FIG. 10) into the cylinder 90 to separate the distal end of the rod portion 91 b from the end of the link 73 b. On the other hand, when the port 96 a is closed and the neutral port 96 c and the port 96 b are allowed to communicate with each other, atmospheric air is introduced in the pressure chamber 92 of the negative pressure actuator 72. This causes the rod 91 to move forward (downward in FIG. 10) to bring the distal end of the rod portion 91 b into contact with the end of the link 73 a.

While the distal end of the rod portion 91 b is in contact with the end of the link 73 b, the urging force of the spring 94 acts on the partition wall 81 a through the rod portion 91 b, link 73 b, and rod portion 81 b. At that time, the urging force of the spring 94 serves to reinforce the urging force of the spring 84. Accordingly, the partition wall 81 a of the positive pressure actuator 71 receives the resultant force of the urging forces of the springs 84 and 94. On the other hand, when the distal end of the rod portion 91 b is separated from the end of the link 73 b, the urging force of the spring 94 does not act on the partition wall 81 a. Accordingly, the partition wall 81 a of the positive pressure actuator 71 receives the urging force of only the spring 84.

The opening/closing drive device 70 b is configured as above to switch the negative pressure actuator 72 between an active state and an inactive state to change the urging force acting on the partition wall 81 a of the positive pressure actuator 71, that is, to change the valve opening pressure of the bypass valve 26 (in two stages (150 kPa and 75 kPa) in this embodiment). Thus, the valve opening pressure of the bypass valve 26 is set at the high pressure P1 (150 kPa in this embodiment) when the negative pressure actuator 72 is in the inactive state (an initial state) and set at the low pressure P2 (75 kPa in this embodiment) when the negative pressure actuator 72 is in the active state.

In the exhaust pressure control valve of the third embodiment including the aforementioned opening/closing drive device 70 b, the negative pressure actuator 72 is initially in the inactive state when the filter of the DPF device 3 is to be recovered. The rod 91 is therefore in an advanced position with its distal end contacting the link 73 b. Accordingly, the urging forces of the springs 84 and 94 act on the partition wall 81 a of the positive pressure actuator 71 and hence the valve opening pressure of the bypass valve 26 is set at the high pressure P1.

When the exhaust gas temperature detected by the exhaust gas temperature sensor 2 b exceeds the predetermined temperature, the ECU 4 activates the negative pressure actuator 72. To be concrete, the ECU 4 outputs the drive signal to the three-way electromagnetic valve 96, allowing the port 96 b to close and the neutral port 96 c and the port 96 a to communicate with each other. Simultaneously, the vacuum pump 97 is also activated. Then, the air in the pressure chamber 92 of the actuator 72 is discharged, moving the rod 91 backward (upward in FIG. 10) into the cylinder 90 to separate its distal end from the link 73 b. Accordingly, the partition wall 81 a of the positive pressure actuator 71 receives the urging force of only the spring 84. The valve opening pressure of the bypass valve 26 can therefore be set at the low pressure P2.

In the exhaust pressure control valve of the third embodiment, the rod portion 91 b is in contact with the distal end of the link 73 b during the inactive state of the negative pressure actuator 72, so that the spring 94 exerts a valve closing force on the bypass valve 26 to enhance the valve opening pressure. Accordingly, the valve opening pressure of the bypass valve 26 can be set at the high pressure P1 (equal to the conventional valve opening pressure). During the active state of the negative pressure actuator 72, on the other hand, the rod portion 91 b is separated from the distal end of the link 73, releasing the valve closing force from the bypass valve 26. Accordingly, the valve opening pressure of the bypass valve 26 can be set at the low pressure P2 (lower than the conventional vale opening pressure). The exhaust pressure control valve of the third embodiment can therefore change the valve opening pressure of the bypass valve 26.

According to the exhaust pressure control valve of the third embodiment, consequently, the valve opening pressure of the bypass valve can be reduced in the case where filter recovery is enabled because the temperature of exhaust gas is high or the temperature of exhaust gas has risen so sufficiently high during filter recovery. The pressure of exhaust gas therefore will not increase more than necessary, unlike conventional configuration, the filter recovery does not need consumption of an excessive amount of fuel. This can improve fuel economy and prevent an increase in pressure of exhaust gas more than necessary. Thus, exhaust gas resistance lowers and hence vehicle drivability can be enhanced.

Fourth Embodiment

A fourth embodiment will be described below. This embodiment is substantially identical in configuration to the third embodiment excepting a configuration of an opening/closing drive device for opening and closing a bypass valve. The following explanation will be made on an exhaust pressure control valve of the fourth embodiment referring to FIG. 11 with a focus on differences from the third embodiment by using the same reference signs to similar or identical parts or components to those of the third embodiment. FIG. 11 is a schematic configuration view of an opening/closing drive device of the fourth embodiment.

As shown in FIG. 11, an opening/closing drive device 70 c includes the positive pressure actuator 71, the negative pressure actuator 72, and a link mechanism (73 b and 20) for transmitting motions of the actuators 71 and 72 to the bypass valve 26.

In this opening/closing drive device 70 c, the distal end of the rod portion 81 b of the positive pressure actuator 71 is rotatably attached to a proximal end of a link 73 b. The negative pressure actuator 72 is placed on an opposite side to the positive pressure actuator 71 so that the distal end of the rod portion 91 b can contact with a distal end of the link 73 b (opposite to the proximal end attached to the rod 81). One end of the arm 20 is fixed to the link 73 b between the positive pressure actuator 71 and the negative pressure actuator 72. The other end of the arm 20 is attached with the bypass valve 26. In short, in the opening/closing drive device 70 c, the negative pressure actuator 72 is located on an opposite side (a lower side in FIG. 11) to the opening/closing drive device 70 b of the third embodiment. The entire opening/closing drive device 70 c can therefore be compact to improve vehicle mountability of the exhaust pressure control valve.

In this opening/closing drive device 70 c, when the port 96 b of the three-way electromagnetic valve 96 is closed and the neutral port 96 c and the port 96 a are allowed to communicate with each other and then the vacuum pump 97 is activated, the air in the pressure chamber 92 of the negative pressure actuator 72 is discharged. This causes the rod 91 to move backward (downward in FIG. 11) into the cylinder 90 to separate the distal end of the rod portion 91 b from the end of the link 73 b. On the other hand, when the port 96 a is closed and the neutral port 96 c and the port 96 b are allowed to communicate with each other, atmospheric air is introduced in the pressure chamber 92 of the negative pressure actuator 72. This causes the rod 91 to move forward (upward in FIG. 11) to bring the distal end of the rod portion 91 b into contact with the end of the link 73 b.

While the distal end of the rod portion 91 b is in contact with the end of the link 73 b, the urging force of the spring 94 acts on the partition wall 81 a through the rod portion 91 b, link 73 b, and rod portion 81 b. At that time, the urging force of the spring 94 serves to weaken the urging force of the spring 84. On the other hand, when the distal end of the rod portion 91 b is separated from the end of the link 73 b, the urging force of the spring 94 does not act on the partition wall 81 a. Accordingly, the partition wall 81 a of the positive pressure actuator 71 receives the urging force of only the spring 84. The urging force of the spring 84 is designed to be higher than that in the third embodiment.

The opening/closing drive device 70 c is configured as above to switch the negative pressure actuator 72 between an active state and an inactive state to change the urging force acting on the partition wall 81 a of the positive pressure actuator 71, that is, to change the valve opening pressure of the bypass valve 26 (in two stages (150 kPa and 75 kPa) in this embodiment). Thus, the valve opening pressure of the bypass valve 26 is set at the high pressure P1 (150 kPa in this embodiment) when the negative pressure actuator 72 is in the active state (an initial state) and set at the low pressure P2 (75 kPa in this embodiment) when the negative pressure actuator 72 is in the inactive state.

In the exhaust pressure control valve of the fourth embodiment including the aforementioned opening/closing drive device 70 c, the negative pressure actuator 72 is initially in the active state when the filter of the DPF device 3 is to be recovered. The rod 91 is therefore held in a retracted position in the cylinder 90 with its distal end being apart from the link 73 b. Accordingly, the urging force of only the spring 84 acts on the partition wall 81 a of the positive pressure actuator 71 and hence the valve opening pressure of the bypass valve 26 is set at the high pressure P1.

When the exhaust gas temperature detected by the exhaust gas temperature sensor 2 b exceeds the predetermined temperature, the ECU 4 stops activation of the negative pressure actuator 72. To be concrete, the ECU 4 stops outputting the drive signal to the three-way electromagnetic valve 96, allowing the port 96 b to open and the neutral port 96 c and the port 96 b to communicate with each other. Simultaneously, the vacuum pump 97 is also stopped. Then, the rod 91 is moved forward (upward in FIG. 11) by the urging force of the spring 94 to come into contact with the link 73 b. The urging force of the spring 94 acts on the partition wall 81 a of the positive pressure actuator 71 to weaken the urging force of the spring 84. Thus, the valve opening pressure of the bypass valve 26 is set at the low pressure P2.

In the exhaust pressure control valve of the fourth embodiment, as mentioned above, the rod portion 91 b is held in contact with the end of the link 73 b during the inactive state of the negative pressure actuator 72 of the opening/closing drive device 70 c for opening and closing the bypass valve 26, so that the spring 94 exerts a valve opening force on the bypass valve 26 to reduce the valve opening pressure thereof Accordingly, the valve opening pressure of the bypass valve 26 can be set at the low pressure P2 (lower than the conventional valve opening pressure). During the active state of the negative pressure actuator 72, on the other hand, the rod portion 91 b is separated from the end of the link 73 b to release the valve opening force from the bypass valve 26. Accordingly, the valve opening pressure of the bypass valve 26 can be set at the high pressure P1 (equal to the conventional valve opening pressure). The exhaust pressure control valve of the fourth embodiment can therefore change the valve opening pressure of the bypass valve 26.

According to the exhaust pressure control valve of the fourth embodiment, consequently, the valve opening pressure of the bypass valve can be reduced in the case where filter recovery is enabled because the temperature of exhaust gas is high or the temperature of exhaust gas has risen so sufficiently high during filter recovery. The pressure of exhaust gas therefore will not increase more than necessary, unlike conventional configuration, the filter recovery does not need consumption of an excessive amount of fuel. This can improve fuel economy and prevent an increase in pressure of exhaust gas more than necessary. Thus, exhaust gas resistance lowers and hence vehicle drivability can be enhanced.

Fifth Embodiment

A fifth embodiment will be described below. This embodiment is substantially identical in configuration to the first embodiment excepting a configuration of an opening/closing drive device for opening and closing a bypass valve. The following explanation will be made on an exhaust pressure control valve of the fifth embodiment referring to FIG. 12 with a focus on differences from the first embodiment by using the same reference signs to similar or identical parts or components to those of the first embodiment. FIG. 12 is a schematic configuration view of an opening/closing drive device of the fifth embodiment.

As shown in FIG. 12, an opening/closing drive device 70 d includes an actuator 74 integrally comprising a positive pressure actuator 71 a and a negative pressure actuator 72 b, and a link mechanism (73 and 20) for transmitting motions of the actuator 74 (i.e. the positive pressure actuator 71 a) to the bypass valve 26.

The actuator 74 includes a cylinder 100, the rod 81, and the rod 91. The cylinder 100 is divided into the cylinder 80 and the cylinder 90 by a partition wall 101. The rod 81 has the partition wall 81 a provided at its proximal end and the rod portion 81 b vertically provided on the partition wall 81 a. The rod 81 serves as a power drive element of the positive pressure actuator 71 a. The rod 91 has the partition wall 91 a provided at its proximal end and the rod portion 91 b vertically provided on the partition wall 91 a.

The partition wall 81 a is movably housed in the cylinder 80 and thereby the cylinder 80 is divided into the pressure chamber 82 and the spring chamber 83. The pressure chamber 82 communicates with the exhaust pipe 5 through the exhaust pressure introduction pipe 23 so that exhaust gas flowing in the pipe 5 is introduced into the pressure chamber 82. Furthermore, an elastic member 102 such as an O ring is fixed on an inner circumferential surface of the partition wall 101 to hermetically close the pressure chamber 82 even when the rod 91 slides. The spring 84 is set in a compressed state in the spring chamber 83. This spring 84 urges the partition wall 81 a toward the pressure chamber 82.

The partition wall 91 a is movably housed in the cylinder 90 and thereby the cylinder 90 is divided into the pressure chamber 92 and an air chamber 93. The pressure chamber 92 is connected to the neutral port 96 c through a pipe 95. Of two remaining ports of the three-way electromagnetic valve 96, the port 96 a is connected to the vacuum pump 97 and the other port 96 b connected to atmosphere. The spring 94 is set in a compressed state in the pressure chamber 92. This spring 94 urges the partition wall 91 a toward the air chamber 93.

The rod portion 91 b is placed extending through the partition wall 101 so that the distal end of the rod portion 91 b is positioned in the pressure chamber 82 of the positive pressure actuator 71 a. The partition wall 101 is provided with a seal ring (the elastic member 102) at a portion contact with the rod portion 91 b to prevent gas leakage from the pressure chamber 82. Herein, the partition wall 91 a is urged by the spring 94 toward the air chamber 93 to bring the distal end of the rod portion 91 b into contact with the partition wall 81 a in the pressure chamber 82. In the actuator 74, as above, the positive pressure actuator 71 a and the negative pressure actuator 72 a are arranged in series. In this actuator 74, the distal end of the rod portion 81 b is rotatably fixed to the proximal end of the link 73. One end of the arm 20 is fixed to the distal end of the link 73 and the other end of the arm 20 is attached with the bypass valve 26.

In the opening/closing drive device 70 d having the above configuration, when the port 96 b of the three-way electromagnetic valve 96 is closed and the neutral port 96 c and the port 96 a are allowed to communicate with each other and then the vacuum pump 97 is activated, the air in the pressure chamber 92 of the negative pressure actuator 72 a is discharged. This causes the rod 91 to move backward (upward in FIG. 12) into the cylinder 90 to separate the distal end of the rod portion 91 b from the partition wall 81 a. On the other hand, when the port 96 a is closed and the neutral port 96 c and the port 96 b are allowed to communicate with each other, atmospheric air is introduced in the pressure chamber 92 of the negative pressure actuator 72 a. This causes the rod 91 to move forward (downward in FIG. 12) to bring the distal end of the rod portion 91 b into contact with the partition wall 81 a.

While the distal end of the rod portion 91 b is in contact with the partition wall 81 a, the urging force of the spring 94 acts on the partition wall 81 a through the rod 91. At that time, the urging force of the spring 94 serves to weaken the urging force of the spring 84. On the other hand, when the distal end of the rod portion 91 b is separated from the partition wall 81 a, the urging force of the spring 94 does not act on the partition wall 81 a. Accordingly, the partition wall 81 a of the positive pressure actuator 71 a receives the urging force of only the spring 84. The urging force of the spring 84 is designed to be higher than that of the first embodiment.

The opening/closing drive device 70 d is configured as above to switch the negative pressure actuator 72 a between an active state and an inactive state to change the urging force acting on the partition wall 81 a of the positive pressure actuator 71 a, that is, to change the valve opening pressure of the bypass valve 26 (in two stages (150 kPa and 75 kPa) in this embodiment). Thus, the valve opening pressure of the bypass valve 26 is set at the high pressure P1 (150 kPa in this embodiment) when the negative pressure actuator 72 a is in the active state (an initial state) and set at the low pressure P2 (75 kPa in this embodiment) when the negative pressure actuator 72 a is in the inactive state.

In the exhaust pressure control valve of the fifth embodiment including the aforementioned opening/closing drive device 70 d, the negative pressure actuator 72 a is initially in the active state when the filter of the DPF device 3 is to be recovered. The rod 91 is therefore held in a retracted position with its distal end being apart from the partition wall 81 a. Accordingly, the urging force of only the spring 84 acts on the partition wall 81 a of the positive pressure actuator 71 a and hence the valve opening pressure of the bypass valve 26 is set at the high pressure P1.

When the exhaust gas temperature detected by the exhaust gas temperature sensor 2 b exceeds the predetermined temperature, the ECU 4 stops activation of the negative pressure actuator 72 a. To be concrete, the ECU 4 stops outputting the drive signal to the three-way electromagnetic valve 96, allowing the port 96 b to open and the neutral port 96 c and the port 96 b to communicate with each other. Simultaneously, the vacuum pump 97 is also stopped. Then, the rod 91 is moved forward by the urging force of the spring 94 to come into contact with the partition wall 81 a. The urging force of the spring 94 acts on the partition wall 81 a of the positive pressure actuator 71 a to weaken the urging force of the spring 84. Thus, the valve opening pressure of the bypass valve 26 is set at the low pressure P2.

In the exhaust pressure control valve of the fifth embodiment, as mentioned above, the rod portion 91 b is held in contact with the partition wall 81 a of the positive pressure actuator 71 a during the inactive state of the negative pressure actuator 72 a of the actuator 74 of the opening/closing drive device 70 d for opening and closing the bypass valve 26. Therefore, the spring 94 exerts the valve opening force on the bypass valve 26 to reduce the valve opening pressure thereof. Accordingly, the valve opening pressure of the bypass valve 26 can be set at the low pressure P2 (lower than the conventional valve opening pressure). During the active state of the negative pressure actuator 72 a, on the other hand, the rod portion 91 b is separated from the partition wall 81 a of the positive pressure actuator 71 a to release the valve opening force from the bypass valve 26. Accordingly, the valve opening pressure of the bypass valve 26 can be set at the high pressure P1 (equal to the conventional valve opening pressure). The exhaust pressure control valve of the fifth embodiment can therefore change the valve opening pressure of the bypass valve 26.

According to the exhaust pressure control valve of the fifth embodiment, consequently, the valve opening pressure of the bypass valve can be reduced in the case where filter recovery is enabled because the temperature of exhaust gas is high or the temperature of exhaust gas has risen so sufficiently high during filter recovery. The pressure of exhaust gas therefore will not increase more than necessary, unlike conventional configuration, the filter recovery does not need consumption of an excessive amount of fuel. This can improve fuel economy and prevent an increase in pressure of exhaust gas more than necessary. Thus, exhaust gas resistance lowers and hence vehicle drivability can be enhanced.

Sixth Embodiment

Finally, a sixth embodiment will be described. This embodiment is substantially identical in configuration to the first embodiment excepting a configuration of an opening/closing drive device for opening and closing a bypass valve. The following explanation will be made on an exhaust pressure control valve of the sixth embodiment referring to FIG. 13 with a focus on differences from the first embodiment by using the same reference signs to similar or identical parts or components to those of the first embodiment. FIG. 13 is a schematic configuration view of an opening/closing drive device of the sixth embodiment.

As shown in FIG. 13, an opening/closing drive device 70 e includes an actuator 75 and a link mechanism (73 and 20) for transmitting motions of the actuator 75 to the bypass valve 26. The actuator 75 includes a casing 76, the rod 91 partly protruding out of the casing 76, and the partition wall (a diaphragm valve element) 91 a slidably attached to an upper end of the rod 91. An outer periphery edge of this partition wall 91 a is tightly held between an upper casing 76 a and a lower casing 76 b. This partition wall 91 a divides the inside of the casing 76 into the pressure chamber 92 and the air chamber 93.

The rod 91 is attached with a spring retainer 99 at some midpoint (at a portion located in the air chamber 93). A spring 94 b is set in a compressed state between the spring retainer 99 and a bottom of the casing 76 (the lower casing 76 b), i.e., in the air chamber 93. This spring 94 b urges the rod 91 toward the pressure chamber 92.

The rod 91 is placed extending through the bottom of the casing 76 with the distal end being connected rotatably to the proximal end of the link 73. The distal end of the link 73 is fixed to one end of the arm 20. The other end of the arm 20 is attached with the bypass valve 26.

The pressure chamber 92 communicates with the neutral port 96 c of the three-way electromagnetic valve 96 through a pipe 95. Of two remaining ports of the three-way electromagnetic valve 96, a port 96 a is connected to the vacuum pump 97 and a port 96 b is connected to atmosphere. In the pressure chamber 92, a spring 94 a is set in a compressed state. This spring 94 a urges the partition wall 91 a toward the air chamber 93. The lower casing 76 b is formed with air inlet ports 77 (two ports in this embodiment) whereby the air chamber 93 is under atmospheric pressure.

In the opening/closing drive device 70 e having the above configuration, when the port 96 b of the three-way electromagnetic valve 96 is closed and the neutral port 96 c and the port 96 a are allowed to communicate with each other and then the vacuum pump 97 is activated, the air in the pressure chamber 92 of the actuator 75 is discharged. Thus the partition wall 91 a is moved upward (toward the pressure chamber 92), separating from the spring retainer 99 (see a chain double-dashed line in FIG. 13). On the other hand, when the port 96 a is closed and the neutral port 96 c and the port 96 b are allowed to communicate with each other, atmospheric air is introduced in the pressure chamber 92 of the actuator 75. Thus the partition wall 91 a is moved downward (toward the air chamber 93) by the urging force of the spring 94 a, coming into contact with the spring retainer 99 (see FIG. 13).

While the partition wall 91 a is in contact with the spring retainer 99, the urging force of the spring 94 a acts on the spring retainer 99. At that time, the urging force of the spring 94 a serves to weaken the urging force of the spring 94 b. On the other hand, when the partition wall 91 a is separated from the spring retainer 99, the urging force of the spring 94 a does not act on the spring retainer 99. Accordingly, the rod 91 of the actuator 75 receives the urging force of only the spring 94 b. The urging force of the spring 94 b is designed to be stronger than that of the spring 94 a.

The opening/closing drive device 70 e is configured as above to switch the actuator 75 between an active state and an inactive state to change the urging force acting on rod 91, that is, to change the valve opening pressure of the bypass valve 26 (in two stages (150 kPa and 75 kPa) in this embodiment). Thus, the valve opening pressure of the bypass valve 26 is set at the high pressure P1 (150 kPa in this embodiment) when the actuator 75 is in the active state (an initial state) and set at the low pressure P2 (75 kPa in this embodiment) when the actuator 75 is in the inactive state.

In the exhaust pressure control valve of the sixth embodiment including the aforementioned opening/closing drive device 70 e, the actuator 75 is initially in the active state when the filter of the DPF device 3 is to be recovered. The partition wall 91 a is therefore in an upper position apart from the spring retainer 99. Accordingly, the urging force of only the spring 94 b acts on the rod 91 and hence the valve opening pressure of the bypass valve 26 is set at the high pressure P1.

When the exhaust gas temperature detected by the exhaust gas temperature sensor 2 b exceeds the predetermined temperature, the ECU 4 stops activation of the actuator 75. To be concrete, the ECU 4 stops outputting the drive signal to the three-way electromagnetic valve 96, allowing the port 96 b to open and the neutral port 96 c and the port 96 b to communicate with each other. Simultaneously, the vacuum pump 97 is also stopped. Thus, the partition wall 91 a is moved downward by the urging force of the spring 94 a to come into contact with the spring retainer 99. The urging force of the spring 94 a acts on the rod 91 of the actuator 75 to weaken the urging force of the spring 94 b. Thus, the valve opening pressure of the bypass valve 26 is set at the low pressure P2.

In the exhaust pressure control valve of the sixth embodiment, as mentioned above, the partition wall 91 a is held in contact with the spring retainer 99 during the inactive state of the actuator 75 of the opening/closing drive device 70 e for opening and closing the bypass valve 26, so that the spring 94 a exerts the valve opening force on the bypass valve 26 to reduce the valve opening pressure thereof. Accordingly, the valve opening pressure of the bypass valve 26 can be set at the low pressure P2 (lower than the conventional valve opening pressure). During the active state of the actuator 75, on the other hand, the partition wall 91 a is separated from the spring retainer 99 to release the valve opening force from the bypass valve 26. Accordingly, the valve opening pressure of the bypass valve 26 can be set at the high pressure P1 (equal to the conventional valve opening pressure). The exhaust pressure control valve of the sixth embodiment can therefore change the valve opening pressure of the bypass valve 26.

Moreover, the opening/closing drive device 70 e does not need to include both the positive and negative pressure actuators shown in the aforementioned opening/closing drive devices. In other words, the opening/closing drive device 70 e needs no positive pressure actuator. Since no positive pressure actuator is required, any pipe for introducing exhaust gas to a positive pressure actuator is also unnecessary. The opening/closing drive device 70 e can therefore achieve an inexpensive opening/closing drive device.

According to the exhaust pressure control valve of the sixth embodiment, the valve opening pressure of the bypass valve can be reduced in the case where filter recovery is enabled because the temperature of exhaust gas is high or the temperature of exhaust gas has risen sufficiently high during filter recovery. The pressure of exhaust gas therefore will not increase more than necessary, unlike conventional configuration, the filter recovery does not need consumption of an excessive amount of fuel. This can improve fuel economy and prevent an increase in pressure of exhaust gas more than necessary. Thus, exhaust gas resistance lowers and hence vehicle drivability can be enhanced.

The present invention is not limited to the above embodiment(s) and may be embodied in other specific forms without departing from the essential characteristics thereof. For instance, the above embodiments exemplify a configuration including a single negative pressure actuator serving as a valve opening pressure changing device, which may include two or more actuators.

In the above embodiments, the three-way electromagnetic valve 47 and the three-way electromagnetic valve 96 are connected to different vacuum pumps respectively. Alternatively, they may be connected to a common (single) vacuum pump.

In the above embodiments, the negative pressure actuator is operated based on the exhaust gas temperature. An alternative is to operate the negative pressure actuator based on the number of engine revolutions, an amount of fuel to be supplied, or the like, instead of the exhaust gas temperature.

Although the air inlet ports 77 are formed in the lower casing 76 at two position in the sixth embodiment, the air inlet port(s) 77 may be formed in the lower casing 76 at one position or three or more positions.

While the presently preferred embodiment of the present invention has been shown and described, it is to be understood that this disclosure is for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims. 

1. An exhaust pressure control valve to be placed in an exhaust gas passage of an internal combustion engine for controlling pressure of exhaust gas to be discharged from the engine, the exhaust pressure control valve comprising: a housing formed with a main passage and a bypass passage; a main valve arranged to open and close the main passage; a bypass valve arranged to open and close the bypass passage; and an opening/closing drive device for opening and closing the bypass valve; wherein the opening/closing drive device includes: a bypass valve opening/closing device for opening and closing the bypass valve; and a valve opening pressure changing device for changing valve opening pressure of the bypass valve.
 2. The exhaust pressure control valve according to claim 1, wherein the valve opening pressure changing device comprises at least one actuator and is adapted to change the valve opening pressure of the bypass valve by setting an operation start pressure of the bypass valve opening/closing device higher than an initial set pressure and exerting a valve closing force that enhances the valve opening pressure of the bypass valve onto the bypass valve opening/closing device during an inactive state of the actuator, and releasing the valve closing force from the bypass valve opening/closing device during an active state of the actuator.
 3. The exhaust pressure control valve according to claim 2, wherein the actuator comprises: an introduction pipe for introducing pressure; a pressure chamber for holding the pressure introduced therein through the pressure introduction pipe; a movable member which forms part of the pressure chamber and can be displaced with the pressure changes; an elastic member placed in a compressed state in the pressure chamber; and a rod connected to the movable member and can be moved in association with displacement of the movable member.
 4. The exhaust pressure control valve according to claim 3, further comprising a ling member, wherein the bypass valve includes a valve element and an arm attached to the valve element, the arm is fixed to the link member rotatably coupled to the bypass valve opening/closing device, and the valve opening pressure changing device is adapted to change the valve opening pressure of the bypass valve by moving the rod into or out of contact with the link member.
 5. The exhaust pressure control valve according to claim 3, further comprising: a ling member; and a power drive element in the bypass valve opening/closing device, wherein the bypass valve includes a valve element and an arm attached to the valve element, the arm is fixed to one end of the link member and the other end of the link member is rotatably coupled to the bypass valve opening/closing device, and the valve opening pressure changing device is placed on the same side as the bypass valve opening/closing device relative to the link member and in series with the bypass valve opening/closing device so that the rod is moved into or out of contact with the power drive element.
 6. The exhaust pressure control valve according to claim 4, wherein the arm is attached to one end of the link member and the bypass valve opening/closing device is coupled to the other end of the link member, and the valve opening pressure changing device is placed on an opposite side to the bypass valve opening/closing device relative to the link member and arranged so that the rod is moved into or out of contact with a connection part between the link member and the bypass valve opening/closing device.
 7. The exhaust pressure control valve according to claim 4, wherein the arm is attached to one end of the link member, the valve opening pressure changing device is placed on the same side as the bypass valve opening/closing device relative to the link member and arranged so that the rod is moved into or out of contact with the other end of the link member, and the bypass valve opening/closing device is coupled to the link member between a portion fixed to the arm and a portion contacting with the rod.
 8. The exhaust pressure control valve according to claim 4, wherein the bypass valve opening/closing device is coupled to one end of the link member, the valve opening pressure changing device is placed on the same side as the bypass valve opening/closing device relative to the link member and arranged so that the rod is moved into or out of contact with the other end of the link member, and the arm is fixed to the link member between a portion connected with the bypass valve opening/closing device and a portion contacting with the rod.
 9. The exhaust pressure control valve according to claim 4, wherein the bypass valve opening/closing device is coupled to one end of the link member, the valve opening pressure changing device is placed on an opposite side to the bypass valve opening/closing device relative to the link member and arranged so that the rod is moved into or out of contact with the other end of the link member, and the arm is fixed to the link member between a portion connected with the bypass valve opening/closing device and a portion contacting with the rod.
 10. The exhaust pressure control valve according to claim 1, wherein the valve opening pressure changing device comprises at least one actuator and is adapted to change valve opening pressure of the bypass valve by setting an operation start pressure of the bypass valve opening/closing device lower than an initial set pressure and exerting a valve opening force that reduces valve opening pressure of the bypass valve onto the bypass valve opening/closing device during an inactive state of the actuator, and releasing the valve opening force from the bypass valve opening/closing device during an active state of the actuator.
 11. The exhaust pressure control valve according to claim 10, wherein the actuator comprises: an introduction pipe for introducing pressure; a pressure chamber for holding the pressure introduced therein through the pressure introduction pipe; a movable member which forms part of the pressure chamber and can be displaced with the pressure changes; an elastic member placed in a compressed state in the pressure chamber; and a rod connected to the movable member and can be moved in association with displacement of the movable member.
 12. The exhaust pressure control valve according to claim 11, further comprising a ling member, wherein the bypass valve includes a valve element and an arm attached to the valve element, the arm is fixed to the link member rotatably coupled to the bypass valve opening/closing device, and the valve opening pressure changing device is adapted to change the valve opening pressure of the bypass valve by moving the rod into or out of contact with the link member.
 13. The exhaust pressure control valve according to claim 11, further comprising: a ling member; and a power drive element in the bypass valve opening/closing device, wherein the bypass valve includes a valve element and an arm attached to the valve element, the arm is fixed to one end of the link member and the other end of the link member is rotatably coupled to the bypass valve opening/closing device, and the valve opening pressure changing device is placed on the same side as the bypass valve opening/closing device relative to the link member and in series with the bypass valve opening/closing device so that the rod is moved into or out of contact with the power drive element.
 14. The exhaust pressure control valve according to claim 12, wherein the arm is attached to one end of the link member and the bypass valve opening/closing device is coupled to the other end of the link member, and the valve opening pressure changing device is placed on an opposite side to the bypass valve opening/closing device relative to the link member and arranged so that the rod is moved into or out of contact with a connection part between the link member and the bypass valve opening/closing device.
 15. The exhaust pressure control valve according to claim 12, wherein the arm is attached to one end of the link member, the valve opening pressure changing device is placed on the same side as the bypass valve opening/closing device relative to the link member and arranged so that the rod is moved into or out of contact with the other end of the link member, and the bypass valve opening/closing device is coupled to the link member between a portion fixed to the arm and a portion contacting with the rod.
 16. The exhaust pressure control valve according to claim 12, wherein the bypass valve opening/closing device is coupled to one end of the link member, the valve opening pressure changing device is placed on the same side as the bypass valve opening/closing device relative to the link member and arranged so that the rod is moved into or out of contact with the other end of the link member, and the arm is fixed to the link member between a portion connected with the bypass valve opening/closing device and a portion contacting with the rod.
 17. The exhaust pressure control valve according to claim 12, wherein the bypass valve opening/closing device is coupled to one end of the link member, the valve opening pressure changing device is placed on an opposite side to the bypass valve opening/closing device relative to the link member and arranged so that the rod is moved into or out of contact with the other end of the link member, and the arm is fixed to the link member between a portion connected with the bypass valve opening/closing device and a portion contacting with the rod.
 18. An exhaust pressure control apparatus comprising: an exhaust pressure control valve set forth in claim 1; and a diesel particulate filter (DPF) device to be mounted in an exhaust gas passage of an internal combustion engine for purifying exhaust gas discharged from the engine, wherein the DPF device is placed upstream of the exhaust pressure control valve. 